Fetal hypoxia. Birth asphyxia. Sakharova Inna. Ye., MD, PhD.

Fetal hypoxia. Birth asphyxia.

Sakharova Inna. Ye., MD, PhD

Plan of the lecture:

1. Definition of birth asphyxia.2. Ethiology of fetal hypoxia and

birth asphyxia.3. Classification of asphyxia.4. Resuscitation of a newborns. 5. Birth asphyxia consequences.

Asphyxia neonatorum is respiratory failure in the newborn, a condition caused by the inadequate intake of oxygen before, during, or just after birth.

Report of the Health Care Committee Expert Panel on Perinatal Morbidity defined

'perinatal asphyxia' as "a condition in the neonate where there

is the following combination: An event or condition during the

perinatal period that is likely to severely reduce oxygen delivery and lead to acidosis,

A failure of function of at least two organs (may include lung, heart, liver, brain, kidneys and hematological) consistent with the effects of acute asphyxia."

Asphyxia neonatorum, also called birth or newborn asphyxia, is defined as a failure to start regular respiration within a minute of birth.

Birth kardiorespiratory depression – syndrom of early (in birth, during the first minutes of life) depression of the main vital functions, including bradycardia, reduced muscle tone, hypoventilation, hypotension, but usually without hypoxemia and hypercarbia. As a rule in the newborn are present one or two signs of these vital functions depression and Apgar score of 4-6 at the first minute.

There are two main types of neonatal asphyxia:

• Acute asphyxia – neonatal asphyxia, which was caused by intranatal factors only.

• Asphyxia, which was developed on the background of prolonged fetal hypoxia associated with placental insufficiency.

The high risk factors of fetal

(antenatal) hypoxia development: 1.Maternal age of less than 16 years old or

over 40 years old.2. Postmaturity.3.Prolonged (> 4 weeks) gestosis of

pregnancy.4. Multiple pregnancy.5. Threatened preterm labor.6. Diabetes mellitus in pregnant women.7. Bleedings and infectious diseases in II-III

trimester of pregnancy.

8. Severe somatic diseases in pregnant women.

9. Smoking or drug addiction in pregnant women.

10. Intrauterine growth restriction or another diseases revealed in fetus in ultrasound examination.

The high risk factors of acute (intranatal) asphyxia

development:1. Cesarean operation (planned or

urgent).2.Malpresentation (breech, pelvic

presentation).3. Premature or retarded birth.4.Waterless period > 24 or < 6 hours,

accelerated labor - < 4 hours in primipara or < 2 hours in secundipara.

5. Placental abruption.6. Obstetrical forceps or vacuum-

extractor use.

7. Birth trauma.8. Congenital malformations of fetus.9. Acute labor hypoxia in mother

(shock, amniotic fluid embolism, poisonings, decompensated diseases).

10. Maternal anesthesia (both the intravenous drugs and the anesthetic gases cross the placenta and may sedate the fetus).

There are 5 basic pathogenetic mechanisms which lead to the

development of the acute

asphyxia neonatorum:

1) Blood flow interraption through the umbilical cord (tight umbilical cord entanglement around of a neck - loop of cord)

2) Disturbances of gaseous exchange through the placenta (placental abruption, placental presentation)

3)     Unequal blood supply of the maternal part of placenta (very intensive labour activity, hypertension of any etiology in mother)

4)     Worsening of blood oxygenation in mother (anemia, cardio-vascular diseases, respiratory insufficiency)

5)     Failure of respiratory efforts of the newborn (iatrogenic – drug induced, caused by congenital malformations).

Apgar score assesment

7-10 – No or mild depression

4-6 – Moderate depression

0-3 – Severe asphyxia

SIGN SCORE

0 1 2

Heart rate Absent Less than 100/min

Over 100/min

Respiratory effort

Absent Weak/irre-gular

Strong/re-gular

Muscle tone

Atony Some flexion

Active movement

Reflex irritability

No response

Grimace Cough or sneeze

Color Universal cyanosis or pallor

Pink body, acrocyano-sis

Completely pink

If Apgar score is 0-3 at the first minute – neonatal mortality is 5,6 %. Nelson and Ellenberg examined Apgar scores in 49 000 infants. Of infants with an Apgar score 0 - 3 at 20 minutes, 59% of survivors died before 1 year, and 57% of the survivors had cerebral palsy. If Apgar score is 0-3 at the first minute and becomes 4 and more in the 5-th minute – possibility of cerebral palsy is 1 %.

Per the guidelines of the American Academy of Pediatrics (AAP) and the American College of Obstetrics and

Gynecology (ACOG), all of the following must be present for the designation of

asphyxia (1992):

• Profound metabolic or mixed acidemia (pH <7.00) in an umbilical artery blood sample, if obtained

• Persistence of an Apgar score of 0-3 for longer than 5 minutes

• Neonatal neurologic sequelae (eg, seizures, coma, hypotonia)

• Multiple organ involvement (eg, of the kidney, lungs, liver, heart, intestines)

ICD (Geneva, 1980): Moderate birth asphyxia – adequate breathing

wasn’t established during the first minute after birth, but heart rate is 100 per minute and more; there is decreased muscle tone and poor reflex irritability. Apgar score is 4-6 at the first minute. “Blue asphyxia”.

Severe birth asphyxia heart rate is less than 100 per minute, breathing is absent or labored (gasping breathing), skin is pale, muscle atony. Apgar score is 0-3 at the first minute. “White asphyxia”.

Clinical manifestations of birth

asphyxia. Before delivery, symptoms may

include: Abnormal heart rate or rhythm

Increased movements of fetus

At birth, symptoms may include: Physiological newborns reflexes are

depressed Hyperstesia Meconium in the amniotic fluid Arterial hypotension Bubbling ( moist ) rales over the lungs Hepatomegaly Fluid, electrolyte and metabolic

abnormalities including hyperkalaemia, hypoglycaemia, and acidosis.

Basic algorithm for newborn resuscitation

Basic algorithm for newborn resuscitation

Step 1. Step 2. -Clear of Meconium? -Provide warmth -Breathing or crying? -Position; clear airway (as necessary)-Good muscle tone? -Dry, stimulate, -Color pink? reposition-Term gestation? -Give O2 (as necessary)Step 3. Evaluate respirations,heart rate, and colorStep 1 + Step 2 = Step A Step A Step 3 =???=Step B

Basic algorithm for newborn resuscitation

Step 4 (or Step B) Provide positive-pressureVentilationStep 5 (or Step C)Provide positive-pressureVentilationAdminister chest compressions Step 6 (or Step D)Administer epinephrine, NaCl, NaHCO3,

narcan

Hypoxic ischaemic encephalopathy

classification of Sarnat and

Sarnat: Grade 1: mild encephalopathy with infant hyperalert, irritable, and over-sensitive to stimulation. There is evidence of sympathetic over-stimulation with tachycardia, dilated pupils and jitteriness. The EEG is normal.

Grade 2: moderate encephalopathy with the infant displaying lethargy, hypotonia and proximal weakness. There is parasympathetic overstimulation with low resting heart rate, small pupils, and copious secretions. The EEG is abnormal and 70% of infants will have seizures.

Grade 3: severe encephalopathy with a stuporous, flaccid infant, and absent reflexes. The infant may have seizures and has an abnormal EEG with decreased background activity and/or voltage suppression.